Why the following test is always faster for the first case?

I was testing the performance of two different approaches to handling streams of integers (primitives). To my surprise, the first test case is always slower, no matter the order.

public void intStreamTest() {
    final int[] ints = new int[1000];
    for (int x = 0; x < 1000; x++) {
        ints[x] = new Random().nextInt(1000);
    }
    // T1
    long start = System.currentTimeMillis();
    for (int x = 0; x <= 10000; x++) {
        List<Integer> result =
            IntStream.of(ints).boxed().collect(Collectors.toList());
    }
    System.out.println("T1 " + (System.currentTimeMillis() - start));
    // T2
    long start2 = System.currentTimeMillis();
    for (int x = 0; x <= 10000; x++) {
        List<Integer> result =
            IntStream.of(ints).mapToObj(Integer::valueOf).collect(Collectors.toList());
    }
    System.out.println("T2 " + (System.currentTimeMillis() - start2));
}

Here is an example of the output:

T1 150
T2 95

When I change the order of test cases (swap sections T2 and T1) I get:

T2 153
T1 92

Did I make a mistake? How is it possible that a second test case is always faster (approx by 60%)?